The technical field of this invention relates to zoned residential Heating Ventilation and Air Conditioning (HVAC) and lighting controls that employ embedded systems and wireless communications. HVAC systems use a large proportion of a building's energy usage and need to be optimized for both environmental and economic reasons.
There is a long history of invention and research associated with HVAC technology.
Programmable Thermostats Programmable setback thermostats that can be set by the occupant for set point, reset point and schedule have been available on the market for a number of years [EnergyStar]. In spite of favorable engineering analysis for prospective energy savings, field studies show that real-world field performance is no better than manual thermostats [Sachs] [Shiller] [Cross and Judd]. These studies have been suggested a number of causes including, dead band gap, difficulty of programming, and comfort issues, with the most likely cause being user overriding the energy saving features.
Residential and Light Commercial Zoning: Modern forced air zone control and VAV (Variable Air Volume) extends back decades. The most extensive use to date has been for commercial and industrial applications. There is substantial ongoing research, including that at the CEC as shown in “Advanced Variable Air Volume System Design Guide”[CEC] and Natural Resources. Canada's CANMET Energy Technology Centre (CETC) is currently involved in an ongoing residential zoned research project[CANMET Natural Resources Canada] with the company Ecologix [Ecologix Heating Technologies, Inc]. Home Comfort Zone teaches a basic version of zoned HVAC control[Alles]. Zone HVAC controls and systems are also taught in the patents of [Alles][Girmado][Parker][Jackson] and [Nelson]. These systems, have several failures: 1) they are expensive to install, 2) are even more expensive to retrofit and 3) they make use of a barometric bypass damper that recycles conditioned overpressure air back into the return system causing reduced performance of the central HVAC plant.
Automated diagnostics, performance monitoring and continuous commissioning: The importance of initial commissioning and ongoing monitoring has long been established in buildings[ASHRAE][Bushby][SoCal-Edison]. According to Brambley, “Performance monitoring, automated fault detection and diagnosis, commissioning, optimal control and the use of development environments, design tools and trainers are complementary, and in some respects synergistic technologies that have strong potential to realize significant energy savings and other performance improvements in commercial buildings, including existing buildings. There is a significant body of previous R&D relating to these technologies that indicates their potential, both generically and for specific approaches and methods. In a significant number of cases, there is the opportunity to establish R&D programs and projects that leverage this existing work in order to move relatively quickly to tools that can be deployed in the marketplace.”
Actuated register/damper design: Actuated dampers and registers are very common in commercial and industrial HVAC installations and are occasionally seen in residential use. There are ongoing efforts to advance dampers such as pneumatic bladders [Alles], the technology offered by Zone Comfort as a retrofit option and the ratcheted Nitinol Shape Memory Alloy (SMA) based devices described by [Patel, et al].
Wired Network Technology: Wired electrical communication has been used for decades in residential HVAC controls. The most common use is the simple closure of a 24 VAC circuit to signal a central HVAC plant to turn on. Serial data links, Power Line Communication (PLC) and true networks are common in commercial HVAC application, but have seen limited use in residential HVAC. An example of a serial protocol is RS-232C. Examples of a of a wired network used in HVAC are BACNET and CANNET.
Wireless Technology: IEEE 802.15.4/ZigBee[IEEE][ZigBee Alliance] was essentially designed for sensor, command and control application such as residential HVAC. Other wireless technologies such as Z-Wave and Bluetooth are also in the marketplace.
Occupancy Sensors Industrial and commercial HVAC systems have long used occupancy sensors and some limited use has been seen in residential settings [Seymour][Simmions][Keating][Disser][Bilger][Gutta][Gua][Mozer].
Occupancy Prediction While scheduled occupancy has been wide spread for both residential and commercial use (see programmable thermostats above), sensor based predictive occupancy has not seen commercial success. Mozer teaches a concept of a Neurothermostat in his prototype “Adaptive Control of Home Environment,” system that includes HVAC, domestic hot water and lighting control. The Neurothermstat makes use of a PC based neural network and X10 sensors and controls. Mozer reports that the X10 communication protocol adds too much latency for his application. The Mozer design uses standard neuro-network train with energy use and occupancy error as feed back values.